RtpPacket.py

import sys
from time import time

HEADER_SIZE = 12

class RtpPacket:
    header = bytearray(HEADER_SIZE)

    def __init__(self):
        pass


    def encode(self, version, padding, extension, cc, seqnum, marker, pt, ssrc, payload):
        """Encode the RTP packet with header fields and payload."""
        timestamp = int(time())
        header = bytearray(HEADER_SIZE)

        # --------------
        # TO COMPLETE
        # --------------
        # Fill the header bytearray with RTP header fields
        #***********************************************
        currFree = 7
        header[0] = header[0] | version << (currFree - 2); currFree -= 2
        header[0] = header[0] | padding << (currFree - 1); currFree -= 1
        header[0] = header[0] | extension << (currFree - 1); currFree -= 1
        header[0] = header[0] | cc; currFree = 7
        #***********************************************
        header[1] = header[1] | marker << (currFree - 1); currFree -= 1
        header[1] = header[1] | pt; currFree = 7
        #***********************************************
        header[2] = seqnum >> 8 & 0xFF
        header[3] = seqnum & 0xFF
        #***********************************************
        header[4] = timestamp >> (8 * 3) & 0xFF
        header[5] = timestamp >> (8 * 2) & 0xFF
        header[6] = timestamp >> (8 * 1) & 0xFF
        header[7] = timestamp & 0xFF
        #***********************************************
        header[8] = ssrc >> (8 * 3) & 0xFF
        header[9] = ssrc >> (8 * 2) & 0xFF
        header[10] = ssrc >> (8 * 1) & 0xFF
        header[11] = ssrc & 0xFF

        self.header = header
        # Get the payload from the argument
        self.payload = payload

    def decode(self, byteStream):
        """Decode the RTP packet."""
        self.header = bytearray(byteStream[:HEADER_SIZE])
        self.payload = byteStream[HEADER_SIZE:]

    def version(self):
        """Return RTP version."""
        return int(self.header[0] >> 6)


    def seqNum(self):
        """Return sequence (frame) number."""
        seqNum = self.header[2] << 8 | self.header[3]
        return int(seqNum)

    def timestamp(self):
        """Return timestamp."""
        timestamp = self.header[4] << 24 | self.header[5] << 16 | self.header[6] << 8 | self.header[7]
        return int(timestamp)


    def payloadType(self):
        """Return payload type."""
        pt = self.header[1] & 127
        return int(pt)


    def getPayload(self):
        """Return payload."""
        return self.payload


    def getPacket(self):
        """Return RTP packet."""
        return self.header + self.payload